The technical field is integrated circuit design.
In integrated circuits, and in particular, very large scale integrated (VLSI) circuits, power (i.e., ground (GND) and supply (VDD)) must be supplied from the power supply and ground to various metal layers that comprise the circuit. The process of creating the required power pathway, or power grid, is called power strapping.
Current power strapping methods and systems rely on one of two approaches. First, the power grid may be created manually each time a circuit is created, or re-created. This approach carries a high maintenance overhead, and cannot be accomplished quickly. A second, or rule-based approach relies on fixed definitions or rules for creation of the power grid. The rule-based approach is automated, and thus has advantages over the manual approach. However, the rule-based approach may work only for a small number of circuits, and different rules and definitions may be required for other integrated circuit designs. Furthermore, the rule-based approach may waste valuable resources by designating power strapping shapes that are larger than what is actually required to distribute power to the circuit.
In many VLSI circuits, a portion of the VLSI design includes regular, tiled arrays of cells. The cell arrays may include power rails that need to be connected to top-level power lines. A method and an apparatus allow automatic creation of the artwork needed to distribute power from the top-level power grid (i.e., lines VDD and GND) to power rails in the cells"" lower-level metal layers. The method and apparatus may be used in conjunction with software tools used to create other elements of the VLSI design. The method and apparatus automate the task of connecting each of the cells in the array to the power lines.
The method begins by identifying, or setting up, all cell power rails. Then, working from the cell power rails to the top metal layer power grid, intersections between resources in the adjacent metal layers are defined. Using the intersections, power strapping shapes are defined within the available resources. The result is a network or power grid from the top-level power lines down to the power rails in the cells.